Method of freeze dehydration of liquid substances



y 3, 1951 E. PwwENzELBERGER 2,559,205

METHOD OF FREEZE DEHYDRATION 0F LIQUID SUBSTANCES Filed Dec. 13, 1949(mm m1 R E 6 mm TB NL EE VZ NN E W H- 527 M: a

Patented July 3, 1951 METHOD OF FREEZE DEHYDRATION OF LIQUID SUBSTANCESElwood Paul Wenzelberger, Dayton, Ohio, as-

signor to The Commonwealth Engineering Company of Ohio, Dayton, Ohio, acorporation of Ohio Application December 13, 1949, Serial No. 132,641

3 Claims. (01. 62-424) This invention relates to a method of dehydrationby freezing the solvent of solutions and/or suspensions.

More particularly, it relates to low temperature dehydration of fluidsbearing heat sensitive constituents.

It is a particular object of my invention to provide a rapid andeconomical means and a method of removing water from fruit juices, beer,wines, pharmaceuticals such as antibiotics, heat sensitive resins,coffee, milk, and vegetable juices. This list is not exclusive, but ismerely supplementary.

It is'also an object of this invention to provide a method wherein ajuice is progressively frozen at temperatures which result in formationof fine crystals of ice, readily separable from the juice.

The concentrate from a first freezing operation then is delivered icefree, or in a condition in which there is a small amount of seed ice, tothe next successive freezing step carried out at a lower temperature.

This results in a concentrate from which nothing has been removed exceptthe Water, and the water removal has been effected without detriment tothe vitamins, volatile oils, tastes, or other characteristics of theproduct.

It is a further object to reduce the power load and the time factor inprocessing by eliminating the necessity for very low sub-zerotemperatures.

It is also an object to eliminate the time element and power factor inthe use of heat and vacuum. a

It is an object to provide a method in which a liquid having a certainpercentage of solids will have its temperature reduced from itsapproximate initial ice forming point by stages while, at the same time,preventing the formation of white ice and of solid freezing through theproduction of relatively small ice crystals, substantially free ofsolids, due to the material being kept in a state of agitation.

It is an object to associate with this stage system a high volume heatexchange capacity in association with means for rapidly changing theliquid interface in contact with freezing surfaces with means for amplecooling or freezing area and with means for providing a flow ofrefrigerant capable of removing the heat as fast as it is absorbed. Theice thus formed is a fine crystalline ice slush having a large icecrystal area and continuous movement for further reseeding and formationof ice crystals for the extraction of water.

It is an addition object to provide that the difference in temperaturebetween the refrigerant and the juice is also the approximate differencein number of degrees between the temperatures of the liquid compositionin the difierent stages.

It will be observed in this process instead of using a very lowtemperature and endeavoring to reduce the temperature as fast aspossible to.

get the maximum freezing, this process uses the opposite course of arelatively small differential between the temperature of the liquidbearing the solids and therefrigerants and a small differential betweenthe stages and the major portion of the stages being at a temperatureusually above zero degrees Fahrenheit.

It is a further object to provide means of agitation to prevent theadherence of ice to the walls of the container, to maintain the ice in astate of continually controlled agitation so that the crystal growth isprovided between ice crystals so that the ice can be removed with aminimum of juice and solids entrained or accumulated by the ice. Thisalso facilitates the movement of the juice and ice to a centrifuge.

It is a further object to provide a common header for the receipt of thejuice and ice from the several stages and a common centrifuge forseparation of the ice from the concentrated juice.

It is also an object to return the juice from .the first stage to thesecond stage and from the second stage to the thirdstage in ice freecondition.

It is an additional object to utilize the ice and ice water forreductionof the refrigeration load and for use in the initial precooling of theraw juice supply.

It is an object of this invention to provide a series of containers, thetemperature of each container being lower than the temperature of thepreceding container of the series, to utilize the ice in one container,to partially reseed the dehydrated juice in the next container, and toselectively remove the juice from each container independently of theother containers and remove the ice from the juice so removed and returnthe concentrated juice to the next container ice free or substantiallyice free, and ultimately to remove the finally dehydrated juice forpacking.

It is a further object to provide for rapid dehydration through rapidcrystal formation by having the large crystals aggregates broken byagitation into small crystals.

It is to be understood that, if white ice forms, it is exceedinglydifiicult to remove and has a tendency to clog and plug the mechanismand causes great difliculty in entrainment of juices and solids.

.ample to fortify the juice when dehydrated by adding about 25 per centof raw juice.

. Concentration by my method can be carried to a high degree withv noinjury to the juice; and it can be reconstituted in the hands of theuser by the addition of requisite water. Nothing is lost from the juiceexcept water and nothing isadded. Heat is eliminated so as not todisturb heat sensitive materials being processed.

In the light of the foregoing, the drawings illustrating one form of themechanism for practice in this process will be more fully understood.

Referring to the drawings:

Figure 1 is a diagrammatic'view of the complete mechanism for continuousand progressive dehydration;

Figure 2 is a view of the automatic electric control system; and

Figure 3 is a detailed view of a valve used at the bottom of thedischarge freezing tanks.

It will be observed that the process of this invention is based on theprinciple of pure ice crystal growth and the removal of these ice watercrystals from the mother liquor in stages.

The principle involved in my step freeze method is based on the theorythat pure ice can be formed as crystals in flotation by controlling thefreezing and agitation conditions so that there is a relatively smalldifferential between the ice forming point of the solution and therefrigerating medium, amounting to about a 5 differential.

It is also based upon the fast formation of ice and the regulation ofice crystal size to avoid formation of white ice which occludes solids,freezes to large agglomerates and prevents clean separations of ice andliquid.

When there is a relatively small differentialrate of heat transferred tothe refrigerating medium.

again form in the solution. The result of this repetitive operation isto produce gradual but uniform crystal growth.

If this uniform heat transfer could be accomplished without anyagitation, large crystals would form. The type of agitation I usecreates small crystals and serves two other functions.

A wiping blade agitator removes any ice which otherwise would cling tothe cold sides of the vessel. This is removed as fast as it forms. Thisice immediately acts as a, seeding process to grow more crystalsthroughout the volume of the liquid.

This wiping agitation is performed by a relatively slow speed agitatorof about 125R. P. M.

The other agitator (at higher speed, i. e., about 800 to 900 R. P. M.)prevents large crystal growth, producing small, pure ice crystals. Italso prevents the crystals so formed from floating to the top of theliquid where they would aggregate and coalesce together, to form a solidmass of ice which wouldocclude juice.

By forming large numbers of individual small crystals, continually inmotion in the liquid, they remain unattached to each other with auniform dispersion of ice crystals in the liquid medium. Being a liquidwith ice slush it becomes easy to transport it or flow it through pipesfrom one piece of apparatus to another.

The tabulation givenlater is suggestive of the ratio of temperatures. Ithas been found that these temperatures, while typical, represent a ruleof action that secures the desired result.

The maintenance of temperatures, which are continuallybeing lowered,maintains the ice as individual crystals, solid in form and easilycentrifuged. This is in marked distinction to the results obtained wherethe ice is warmed for partial melting or where white ice is formedhaving juice and solids occluded therein and the ice takes on a physicalcharacter which will disrupt the process.

I have found that by first cooling a liquid bearing solids and adjustingthe difference between the temperature of the liquid and the temperatureof the refrigerant by a small differential of approximately 5 and thenagitate the liquid bearing the solids or seed with ice crysals or both,the liquid will immediately form ice very rapidly and the temperaturerise back to the ice forming or congealing point. To prevent such ice soforming, occluding some of the solu- The heat transfer, it has beenfound, can be effected while maintaining small temperaturedifierentials, if a ratio of one square foot of refrigerating surfacefor each one to one. and a half gallons or less of liquid is maintained.

When such ratios are held substantially constant, the time period, forexample, 12 to 20 minutes, remains substantially constant regardless ofthe quantity of liquid being processed.

To be commercially feasible the process must have a high volumecapacity. In this system the capacity is great because the time intervalfor maximum ice formation is under direct control at all times and theseries of containers integrated in their operation, so that liquid only.stays in each tank long enough for formation of the maximum ice contentor ice crystals of maximum size for that temperature, and as. aconsequence thereof reaches the maximum concentration for that stagebefore the resultant solution is moved to the next container, whosetemperature is lower than the temperature at which ice will tion and thesolids in the ice and to prevent the crystals of ice from growing largeand forming the ice, I provide continuous agitation to prevent coolingand ice formation at the normal congealing point, particularly in largecrystals and in white ice. I secure the result of fine crystals in alarge mass.

I find it desirable to agitate at slow speed in one direction andsimultaneously at high speed in another direction so as to effect themaximum heat transfer at the low differential between the refrigerant onthe outside and the liquid bearing ture, below the ice formingtemperature of the solution. In order to speed the ice crystal formationunder these conditions, the system must possess high heat exchangecapacity. This may be brought about by first, agitation, which bringsabout rapid change of the liquid interface on contact with the freezesurfaces and, secondly. by maintaining a ratio of one square foot ofcooling surface for each one to one and a half gallon of solution beingtreated and, thirdly, by maintaining the flow of refrigerant capable ofremoving a relatively large quantity of heat.

The above process is based upon a system of heat exchange in which a lowdiiierentialis maintained between the ice forming temperature of thesolution and the temperature of the solution. I

I also find it important that. the major portion, in many instance, ofthe stages of progressively lowering the temperature shall be above zeroand I also find it important that the successive stages be at relativelysmall temperature reductions, such as about and 7 F., and that thetemperature of the liquid in the second stage should be approximatelythe temperature of the refrigerant in the first stage and so on. It willbe understood that these differentials will vary with the liquids andthe solids, but the principle of the operation remains the same.

By avoiding extremes of temperature, quick freezing and by maintainingeasy stages of lowering temperatures and modest differentials betweenthe refrigerant and the liquid while causing agitation, a steadyfreezing of small ice crystals will take place and rapid dehydration canbe effected without occludin other liquids and solids than water.

By starting, as in the case of orange juice, at a tank temperature of 23F. above zero, with an outside temperature of 18 F., then a temperaturein the next tank of 18 F., with an outside temperature of 13 F., then atank temperature of 13 F., with an outside temperature of 8 F., and inthe fourth tank, a temperature of 8 F., with an outside temperature of 3F., and in the last tank, a temperature of 3 F., with an outsidetemperature of 2 F., free clear ice crystals can be secured that areeasily maintained by the stirrer, in free movement, with minimum crystalsize and the maximum freezing capacity for the temperature applied. Thisprinciple of a, multiple series of steps, starting the temperature justabout at the freezing point of the juice and progressively reducing itand progressively removing water by freezing, enables this result to besecured.

in order to economize refrigeration, the first two stages are normallyconnected to one compressor and the remaining stages to another.

I is a supply tank for raw juice that is maintained at a temperature ofabout 34 F. through the circulation of ice-water, previously cooled bythe ice, through the jacket 2, supplied by the pipe 3 and dischargedthrough the pipe 4. A cover 5 is maintained over the raw juice and.where desired, air can be eliminated and other steps taken to preservethe material from contamination, bacteriological and enzyme action. Thisice-water is supplied from the melting ice 5 in the tank 1. Therefrigerant at 8 passes through the pipe 9, valve l0, pipe ii, pump l2,valve l3, pipe l4, pipe I5, into pipe 3. l6 indicates a valve for adrain. The waste icewater can be sent to the refrigerating machine forcondensation use or otherwise employed for cooling.

The tank I is provided with a drain pipe ll, controlled by theelectrically operated valve l8. Each of the electrically operatedvalves, of which I8 is one, is connected to a master sequence contacttime i9, which is actuated by a motor whereby the pipe lila dischargesthe juice at about 34 temperature into tank 20, which is surrounded by afreezing chamber 2|, connected to a suitable source of refrigeration andinsulated at 22. The same construction applies to the other tanks. Therefrigeration system is conventional and is not shown.

In each of the tanks there is a motor driven stirrer comprising a pulley23, a shaft 24 and vertical and horizontal stirrer blades 25 and 25. Inorder to facilitate the discharge of the ice and to prevent thedischarge from freezing, the discharge hopper 21 has no refrigeration.It is. therefore, at a higher temperature. Likewise, the discharge pipe28, is controlled by a valve 28 that has no refrigeration and whichvalve is more specifically shown in Figure 3. Valve 29 is actuated by alink mechanism from the solenoid 23a.

The propeller 20a has an 18 pitch. It is driven by a shaft which runsthrough the center of the hollow wiper shaft 20b for keeping the wallsof the container 20 free of ice. The propeller 20a rotates clockwise at600 to 800 R. P. M. pushing downward and the wiper 20b counter-clockwiseat about R. P. M.

The discharge hopper 30 and its drain pipe 3| to the centrifuge 32 areinsulated. The centrifuge operates constantly as one of the tanks isalways discharging into the centrifuge. The ice is discharged throughthe port 33 to the tank I. The ice free, partially dehydrated juice isdischarged from the centrifuge 32 through the pipe 34, pump 35, throughthe pipeline 36, through the valve 31, to the pipe 38, which deliversthe dehydrated juice from the first stage into the tank 33.

Usually some small part of ice is entrained purposely in the tank 39with the incoming juice. If it is not entrained, it is sometimes usefulto seed the juice with ice to facilitate the rapid formation about eachnuclei of ice crystals. The juice passes from the tank 39 through thevalve 40, pipe 4|, to the header 30 and is thence delivered through thecentrifuge in the same manner at: before into the pipe 42, valve 43, tothe third tank 44, where it again passes through a valve 45 and the pipe46, to the header 30. After being centrifuged, the juice passes throughthe valve 41 and pipe 48 to the tank 49. This concentrated juice passesthrough the pipe 50 and valve 5|, to, the header 30. After centrifuging,it passes through the valve 52, pipe 53, to the final tank 54, whence itpasses, in its concentrated form to the valve 55, pipe 56 to thecentrifuge and thence through the valve 51, pipe 58, to the point offinal packing.

Each time the juice is delivered to its respective tank, a freezingperiod is allowed in order to produce a new crop of pure ice crystals,only of sufficient length for the freezing point of the solution to belowered to approximately the temperature in the tank, which are removedin each stage by the centrifuge.

The final product can be either shipped in frozen form in the sense thatit is refrigerated, or it can be packed and preserved withourtrefrigeration if the concentration is more than 60 per cent. The sugarenables preservation to be successfully accomplished over an extendedperiod of time at room temperature. It will be understood suitableprovisions are taken for sanitation, for the prevention of enzyme actionand for the prevention of bacteria and other reasons that might causespoilage.

' The practical operation of the machine in this system and method notonly provides a continuous method, but is a very rapid one in theproduction of dehydrated juice. The formation of ice is very rapid, thecrystals are small, they have very little juice entrained in them, beingmaterially less than a fraction of 1 per cent, and the crystals can bereadily utilized for reseeding where necessary by moving from one tankto another. As the raw juice is being supplied to the supply tankcontinuously, or at intervals, it is possible to have a continuous flowinto the main tank at will, so that all tanks in the system are alwaysoperating; and the centrifuge, which is common to all tanks, is alwaysoperating so that none of the ice or the ice-water is wasted, but all ofit is applied to the refrigeration of the uice.

The problem of the formation of white ice has been overcome and clearcrystal ice is forme by this method. The crystals are small and of greatnumber, possessing the maximum cooling.

area and the maxiinum nuclei to facilitate very rapid freezing. Theslush is formed rapidly and this slush and the dehydrated liquid can beeasily handled by gravity through the system.

FREEZING CONDITIONS AND PROCEDURE Example I .--12% solids-orange juiceInitial ice forming point-28 F. r #1 tankjuice at 23 F., refrigerant 18F. #2 tankjuice at 18 F., refrigerant 13 F. #3 tankjuice at 13 F.,refrigerant 8 F. #4 tankjuice at 8 F., refrigerant 3 F. tankjuice at 3F., refrigerant 2 F.

Example II.10% solids-cider vinegar Initial ice forming point-32 F.

#1 tankjuice at 2'7 F., refrigerant 22 F. #2 tankjuice at 22 F.,refrigerant 17 F. #3 tankjuice at 17 F., refrigerant 12 F. #4 tankjuiceat 12 F., refrigerant 7 F. #5 tankjuice at 7 F., refrigerant 2 F.

Different liquids have different initial congealing points so that atemperature scale is established for each material processed. Varioustemperatures at which ice crystals may form may be used in each or alltanks.

Typical agitation by the wiper blades is caused bya speed of 125 R. P.M. and of the propeller blades of 700-800 R. P. M. These speeds arevaried according to the size of the tank and material being processed.

Suitable mechanism for transferring ice from one tank to another can beemployed, but is not shown. It has been found desirable to select theparticular tank for delivery to the other tanks according to thenecessity for seeding and the type of liquid being processed. Acounterflow of ice, under some conditions, is desirable, but one of theparticular advantages of this method is the very rapid freezing bystirring and agitation.

1 It will be understood that the following claims comprehend variouschanges in temperature,

mechanism, speed of' stirring and procedure acfreezing temperature ofthe liquid at the respective stages that is the same at each stage,establishing the temperature at each stage at an amount lower than thepreceding stage approximately equal to said differential, retaining eachstage under refrigeration at a constant temper- .ature level at the lowtemperature differential established thereon thereby continuouslyforming solvent crystals therein until the freezing temperature of theliquid being cooled approximates the temperature of the refrigerantapplied to the liquid whereat crystal formation ceases, and removingfrom the liquid the solvent crystals formed in each stage before passingthe liquid bearing the solids to the next stage 2. In a method ofdehydration, moving a liquid bearing solids by stages throughprogressive stages of lowering temperature, applying a, refrigerant ateach stage at a differential of temperature between the refrigerant andthe initial freezing temperature of the liquid at the respective stagesthat is the same at each stage while maintaining a refrigerated surfacearea on the liquid of at least one square foot of cooling surface pergallon of solution being treated, establishing the temperature at eachstage atan amount lower than the preceding stage approximately equal tosaid differential, and removing from the liquid the solvent crystalsformed in each stage before passing the liquid bearing solids to thenext stage.

3. In a method of dehydration, moving a liquid bearing solids by stagesthrough progressive stages of lowering temperature, applying arefrigerant at each stage at a differential of temperature between therefrigerant and the initial freezing temperature of the liquid at therespectemperature of the liquid at the same respective stages,establishing the temperature at each stage at an amount lower than thepreceding stage approximately equal to said differential, and removingfrom the liquid the solvent crystals formed in each stage before passingthe liquid bearing solids to the next stage.

ELWOOD PAUL WENZELBERGER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 994,555 Alexander June 6, 19111,738,275 Baker Dec. 3, 1929 2,200,982 Dedlow May 14, 1940 2,324,869Oman July 20, 1943

